Modeling and simulation of sedimentation processes in a lowland river

Sediment load is an ecological criterion for the assessment of water quality as well as dissolved or particle-bound pollutants, governed by sediment transport. In a tidally unaffected section of the Elbe River upstream from Geesthacht a decreasing concentration of suspended particle load was observed during several measuring campaigns and for a few discharge situations. The reduction of suspended sediment seems to be caused by a selfpurification process due to particle settling. To verify this assumption the turbulent sediment transport in this Elbe River reach was simulated applying two- and three-dimensional mathematical models. The transport in rivers can be modeled by the turbulent momentum equations (Reynolds' equations) to determine the velocity field and by special convection-diffusion equations to calculate concentrations of different particle fractions each characterized by a mean settling velocity. Aside from concentration measurements for this river section a few settling velocity spectra were measured simultaneously.